In the manufacture of fiber-based materials used to absorb and contain fluids such as water, milk, coffee or urine, nasal discharge and other body exudates, it is commonly a property of the absorbent materials that they have a low density and corresponding high void volume. The high void volume allows for absorption and containment of the fluid, but leads to products that have a low overall density and occupy substantial volume. This inherent void volume is a characteristic of absorbent materials in that the fluid to be contained needs to reside in most cases in the void volume of the fiber web. Heretofore, most materials currently used in products designed to absorb and contain fluid, while having large void volumes, are inherently low in density and are therefore bulky.
The low density of the materials, while providing the desired performance in the product, also imposes some penalties in the form of bulky, low-density products. For the producer of products, the low density of the absorbent materials imparts a penalty in packaging and transporting of its products. For the converter, it imposes problems in storage, handling and shipping of its final products. For the retailer, it means using a large amount of shelf space for a relatively small number of products. For the ultimate consumer, it means handling, storing and using bulky, low-density materials. For such products as diapers, feminine pads and tissue and towel products, the functionality of the products as absorbents generally outweighs the disadvantages of the bulk imposed by the low density; however, given a choice, most consumers would prefer to have thinner, less bulky products. While the advantages to the consumer are obvious, there are many other advantages that thin, dense, but highly absorbent materials can provide to product design, performance and consumer appeal.